Thin-film rechargeable batteries have numerous applications in the field of microelectronics. For example, thin-film batteries provide active or standby power for microelectronic devices and circuits. Active power sources of the thin-film battery type are used, for example, in implantable medical devices, remote sensors, miniature transmitters, smart cards, and MEMS devices. Standby power sources of the thin-film battery type are used, for example, in PCMCIA cards and other types of CMOS-SRAM memory devices.
In a thin-film battery, a chemical reaction takes place between an anode and cathode by interaction of the anode and cathode through an electrolyte. The attractiveness of thin-film batteries over conventional batteries is that the electrolyte is a substantially solid or non-flowable material rather than a liquid. Liquid electrolytes pose leakage problems and are often highly corrosive. Of the solid electrolytes, thin-film batteries typically employ ceramic electrolytes. Solid electrolytes are desirable in cells or batteries where liquid electrolytes may be undesirable, such as in implantable medical devices. Preferred solid electrolytes include materials that are solid at room temperature, electrically insulative and ionically conductive.
One of the challenges for thin film battery manufacturers is to provide a thin film battery that will have a life of up to 20 years. Such a life is particularly difficult to obtain with thin film batteries containing anode materials which are highly reactive with oxygen and/or water or water vapor. Various barrier materials have been applied to thin film batteries to reduce the reactivity of the anode materials toward oxygen and/or water or water vapor. However, such barrier materials have met with limited success.
As advances are made in microelectronic devices, new uses for thin-film batteries continue to emerge. Along with the new uses, there is a need for high performance thin-film batteries having improved life. In particular, there is a need for rechargeable thin film batteries that have a life approaching 20 years.